Street lighting luminaire



June 28, 1,;949. I T. w. RoLPH 2,474,327

STREET LIGHTING LUMINAIRE Filed May 7, 1946 5 Sheets-Sheet 2 F licl. S d

M DEV/argo 35am INVENTOR THU/was u. PoLP/-l ATTORNEY June 28, 1949. T.w. ROLPH 2,474,327

STREET LIGHTING LUMINAIRE Filed May 7, 1946 5 Sheets-Sheet 3 lNvENToR75l/mms M ROLF/ 1 ATTORNEY Patented June 28, 1949 STREET LIGHTINGLURIINAIRE Thomas W. Rolph, Newark, Ohio, assignor to Holophane Company,Inc., New York, N. Y., a

corporation of Delaware Application May 7,1946, serial No. 667,826

11 claims. (c1. 24o- 106) l The present invention relates to streetlighting luminaires and is more particularly directed toward asymmetricstreet lighting luminaires employing shielding reflectors.

In street lighting luminaires it is customary to employ reflectors ofparabolic contour to produce parallel downwardly directed light rays atan angle which is too steep for lighting remote street areas. Thereflectors extend below the Figures 3 and 4 are side elevational andinverted `plan views of the refractor at a small scale illustrating theYemission of rays from the refractor;

Figure 5 is a diagrammatic view further illustrating light ray control,a fragment being in sectionfon the line 5-5 of Figure 1;

Figures `v6 and 'lare diagrammatic side elevational and inverted planviews of a partly comlight source so that a substantial portion'of'the10 pleted plungernforaise making the refractor downwardly emitted directlight may be directed/s/oi'Figuies 1 to 5;

into controlled directions, and//as/a/result'he reflector shields the...light/source at substantial angles below the horizontal.

The present invention contemplates providing such street lightingequipment with refractors adapted to close the bottom of the reflectorsand redirect the light into higher angles above the nadir and at thesam'e time collect the light into beams adapted for lighting elongatedstreet areas.

According to the present invention, the refractor takes the form of acone of a depth which permits all the reflected light rays to cross theaxis before they are intercepted by the refractor.

This shape makes it possible to employ the small- 25 est possiblerefractor for handling the reflected beam and the straight sides of theconical form have the same angle of incidence with the reflected rays.

In order to obtain the laterally concentrated beams at angles higherthan the vertical angle of the reflected light, it is necessary todeviate the light on each side of a medium plane both laterally andvertically. In practicing the present invention this deviation iscarried out by systems of prisms on the inside of the refractor, theoutside being smooth, except for diffusing flutes. These systems ofprisms are tilted at varying angles so as to effect a varying amount oflateral deviation while obtaining a substantially uniform Verticaldeviation.

Other and further objects will hereinafter appear as the descriptionproceeds.

The accompanying drawings show, for purposes of illustrating the presentinvention, tWo embodiments in which the invention may take form, itbeing understood that the drawings are illustrative of the inventionrather than limiting the same.

In these drawings:

Figure 1 is a vertical sectional view taken on the line l-l of Figure 2,through a street lighting luminaire, illustrating typical ray paths;

Figure 2 is a top plan view of the refractor of the luminaire;

Figure 8 is an inverted plan view of the 'plunger after furthermachining operations;

Figure 9 is a more or less diagrammatic side elevational View of thecompleted plunger; and

Figure 10 illustrates a modified form of refractor.

In Figure 1, the filament of the street lighting lamp is indicated atIll. The lamp is received in an annular parabolic reector I I with adownwardly sloping axis so that all the downwardly reflected rays suchas I2 cross the vertical axis I 3 through the center of the luminaireare at corresponding angles. Angles such as from about 45 to about 55are suitable. The 45 angle is illustrated. Owing to the size ofthelament the light rays spread slightly above and below these rays.

Any closure across the bottom of the reflector which is to intercept thelight only after it has crossed the vertical'axis, would have to be deepenough to accommodate the rays reflected from the lower 'part of thereflector. This determines the vertical depth of the refractor. Whilevarious forms of refractor can be made of the desired depth and outsidediameter, a very desirable form from the point of view of appearance,ease of molding of the glass, and efficiency, is a straight sided cone.

Manufacturing methods necessary for making pressed glass refractors arenot, however, adaptable for making a truly conical refractor withinternal prisms for the purposes desired. The metal molds employed inmaking the pressed glass refractors are made on metal Working machinerywhich is suitable for cutting the metal by turning, planing or millingoperations, suitable for annular or spherical surfaces, or on atsurfaces. Annular prisms on the refractor would be effective to changethe vertical angle of the light rays but would not be effective inchanging the horizontal angle. Furthermore, radial refracting prismswould not be effective for changing the vertical angle.

Reference will now bemade to Figures 6 and 9 inclusive, which indicatethe method of manufacture employed in making the plunger used in moldingthe glass. The turned plunger is indicated at in Figure 6. It is anannular conically shaped plunger of the slope and diameter necessary formaking the piece of glass of the desired thickness when used with a moldof the desired size. It will be obvious that all surfaces of this cone,in planes other than radial, are curved and that they do not have aconstant radius of curvature. The contour is that of an ellipse,hyperbola or parabola, depending upon the direction of the intersectingplane, and hence no tool working from a iixed center is adaptable forcutting along the surface of the cone in any such direction.

s a first step toward providing the plunger with surfaces in which thedesired prismatic forms may be cut, the surfaces of the plunger areplaned or milled to form flat triangular areas occupying a sectorcorresponding with that in which lateral deviation is desired. In theillustrated example, as more clearly shown in Figure 8, seven flat areasor sub-sectors 2| to 21 inclusive, each of 20 angular width, are groupedtogether to form a 140 sector of a pyramid, and seven flat areas 2|' to21' inclusive, are similarly grouped together. Between these flattenedareas the original straight sided cone remains as indicated at 28-28'.This machining operation provides a plunger with a number of flat areas,each of which is available for further machine operations to produce aprofile suitable for the prism forming elements.

The plunger is then put into the proper machine and cuts made acrosseach face of the plunger in the proper direction and at the proper angleto the face to obtain desired control of light rays when the glass isformed. In the side view in Figure 9 the directions of the cuts areindicated by-.the parallel lines in the areas 2i to 21, inclusiva- Itwill be noted vthat the formation of the plunger asit'appears in theelevation of Figure 9, is symmetrical -with respect to a radial medianplane 30. The flat faces 2| to 21 on the opposite' side of the plungerare similarly machined to form similar grooves which are symmetricalwith respect to a radial plane 3| (Figure 8) The conical surfaces 28e-28are machined radially to provide contours suitable for radial prisms orflutes.

Figures 1 and 2 show the refractor produced when the plunger of Figures8 and 9 is employed in aconical mold with straight sides of the sameslope as the sides of the plunger. The upper surface of the refractorhas sectors including areas 2|a to 21a, and 2|a' to 21a' respectively,disposed about a pyramid and each of these areas has a system ofparallel prisms whose directions are indicated in Figures 1 and 2. Theupper conical surface 28a on the street side S of the refractor isprovided with diffusing iiutes 32 while the upper conical surface 28a'on the house side H is provided with radial refracting prisms 33.

It will be seen that the prisms in areas 24a and 25a are alike except asto direction, which is nearly horizontal; that prisms in regions 23aandI 26a are alike, except as to direction, which is further from thehorizontal. Again the prisms in regions 22a and 21a are alike and stillfurther from the horizontal. The prisms in region 2|a are still furtherfrom the horizontal and are preferably crossed by radial prisms asindicated by the radial lines in Figure 2. There is a similar departurein angle from one area to the other on the prismatic surfaces on theright hand side of Figure 2.

If one were to take a section through any one of the areas having theparallel prisms on a plane at right angles to the direction of theprisms, there would be obtained a prism outline the same as thatappearing in the section of Figure 1, except for the differences inprism angle which arise because of the lateral position of the regionrelative to the median plane.

'I'he optical action of the refractor will now be discussed. If one wereto consider the rays reflected from the right hand side of the reflectoracross the axis in the position indicated in Figures l and 2, it will beseen that all these rays in this plane strike the ribbed surface 2|a atangles which aresubstantially normal to the general direction of thissurface. Inasrnuch, however, as

toward median plane 30 and out of the plane of the paper, Figure 2. Thiselevation and lateral deviation takes place with respect to all the raysfalling on area 24a. The same elevation and similar but opposite lateraldeviation, is effected on the rays falling on area 25a, and similarlylateral deviation takes place to a greater extent in areas 23a, 26a, 21aand 2 la.

Owing to the conical configuration of the outside surface of therefractor the lateral deviation of the rays emitted from the refractoris altered from what it would be if the outer surface of the refractorwere also pyramidal. This operation is illustrated in Figures 1 and 5.The extreme rays Ill and 4i crossing the axis of the luminaire andfalling on an area such as 22a, have an angle of divergence from thecenter Il in the vertical axis |3|3 equal to the angular width of theregion 22a when measured in the oblique plane of about |6. The apparentangle of divergence in plan is 20 as in Figure 5. The prisms on theinner surface of the refractor introduce as above described, lateraldeviation and elevation of the rays so that in the glass they havedirections indicated at 40' and 4|', as though coming from 0. Owing tothe fact that the external surface 43 of the refractor has a radius ofcurvature about the axis or center and the prism system on 22a is in afiat plane, the refractor is thicker at the center of region 22a than atits edges. A condensing action, therefore, takes place along with theelevation and lateral deviation caused by the Obliquity of the rays inthe glass to the general direction of the outer surface and the light istransmitted with a reduced angle of divergence as indicated by the lines40"-4i", as though the rays were coming from a more remote verticalsource 0". This has the effect of bringing more of the light toward themedian plane 3| than would have been the case with an externallypolygonal refractor for then the apparent swing of the emitted rayswould have been from a point such as X.

Referring now to Figures 3 and 4, it will be seen that the luminaire isadapted to give two beams such as 505| directed below the horizontal atan'angle of for example 75 to the nadir and converging toward oneanother at an angle of 160, and that light is sent in the desireddirection from the entire surface of the refractor except that occupiedby the zones 28a and 28a on the street and house sides, respectively, ofthe luminaire. The refractin'g prisms 28a on the house side divert thelight from the houses and the diffusing prisms 28a on the street sideplace the light in the adjacent street areas.

In the modified arrangement shown in Figure the area 60 adjacent themedian plane 6l has horizontal prisms, while the laterally disposedareas 63, 63 and 64, 64 have oblique prisms. 'I'he horizontal prisms maybe annular on a conical area or straight on a fiat area, in which casethe condensing action A, Figure 5, takes placewithout additional lateralshift.

What is claimed is:

1. A street lighting' refractor having the general shape of an invertedcircular cone, the upper surface of the refractor being divided intosectors, on opposite sides of a median vertical plane, each sectorincluding a plurality of pyramidally disposed flat areas, each of theseflat areas having a system of parallel light elevating prismatic ridgesof uniform refracting power and running in a direction oblique to thehorizontal, whereby downwardly directed light rays crossing the axis ofthe cone at uniform vertical angles and falling on said system ofprisms, are deviated uniformly vertically and also deviated laterallytoward the median plane, the refracting power of the systems of ridgesincreasing as the flat areas are more remote from the median plane sothat the transmitted rays are directed in the general direction of saidplane.

2. A street lighting refractor as claimed in claim 1, `wherein said fiatareas abut at the median plane so that the light striking the elevatingsurfaces of the ridges is elevated and deviated laterally. -L

, 3. A street lighting refractor as claimed in claim 1, having adjacentthe median plane horizontal prisms which effect elevation of rays only.

,4. A street lighting refractor as claimed in claim 1, wherein the outersurface is a surface of revolution so that the refractor is thickeropposite the middle of each flat area than at its edges whereby thehorizontal divergence of the transmitted rays is reduced below thehorizontal divergence of the incident rays.

5. A refractor of inverted conical shape adapted to receive downwardlydirected light rays of uniform slope in all azimuths about a coaxialvertical axis.after they have crossed said axis, the refractor having aplurality of dihedral sectors, each adapted to receive and transmit thelight rays between two radial planes, each sector being subdivided, andcertain of the subdivisions on opposite sides of the median planethrough the sector, having oblique parallel prisms of uniform refractingpower for uniformly deviating the rays incident thereon into highervertical angles and toward said median plane.

6. A street lighting refractor of inverted conical shape adapted toreceive downwardly directed light rays of uniform slope in all azimuthsabout a coaxial vertical axis after they have crossedsaid axis and attoo steep angles for lighting remote street areas and transmit the lightat higher angles above the horizontal and in radially directed beams,the inner surface of said refractor being symmetrical with respect tothe median planes of the beams, and having a plurality of pyramidallydisposed faces on each side of each median plane, said faces havingsystems of parallel obliquely disposed prisms of uniform refractingpower, the systems being variably disposed to elevate the rays incidentthereon and laterally deviate them toward the median plane, thesteepness of the prisms and their refracting power increasing with theremoteness of the faces from the median plane,

7. A refractor having a conical outer surface, and an inner surface ofpyramidal shape with the same angle of slope as the outer surfacewhereby plano-convex lens elements are formed between the inner andouter surfaces, the surfaces of the faces of the pyramid havingobliquely extending parallel refracting prisms, acting on parallelincident light in radial planes and uniformly deviating the rays in therefractor both angularly about the axis of the cone andwith re- .spectto the axis, so that they reach the outer sur- 8. A refractor havingplano-convex lens elements of triangular shape juxtaposed about avertical axis to forma continuous inverted conical outer surface and acoaxial inner pyramidal surface, the lens elements being of generallyuniform thickness, and each having on their inner surfaces systems ofparallel obliquely disposed prismatic ribs of uniform refracting powerand disposed to deviate incident rays which in radial planes aresubstantially normal to the corresponding pyramidal surface bothlaterally about the vertical axis and vertically toward the horizontal,the opposed outer surface acting to laterally deviate the emitted raysin variable amounts and to vertically elevate them uniformly.

9. A refractor adapted to receive downwardly directed light rays ofuniform slope in all azimuths about a vertical axis after they havecrossed said axis, the refractor having walls at substantially rightangles to the direction of the rays, the inner surfaces of the wallsbeing in the form of ilat triangular areas, said areas having parallellight elevating prisms of uniform refracting power, the prisms in twoadjacent areas sloping upwardly from the median plane between them toswing the emitted rays toward the median plane, the prisms on the areasbeyond the said adjacent areas sloping upwardly at greater angles toswing the rays emitted thereby through a greater angle toward the medianplane.

10. A refractor as claimed in claim 9, wherein the outer surface of therefractor is continuously convex in horizontal planes and reduces thedivergence in horizontal planes of the emitted rays below the divergenceof corresponding rays falling on the opposed at area.

11. A refractor adapted to receive downwardly directed light rays ofuniform slope in all azimuths about a vertical axis after they havecrossed said axis, the refractor having walls at substantially rightangles to the direction of the rays, the inner surfaces of the wallsbeing in the form of ilat triangular areas, said areas having parallellight elevating prisms of uniform refracting power, the prisms on areasequally spaced from the median plane sloping upwardly from the medianlplane between them to swing the emitted rays toward the median plane,the prisms.

on the areas beyond the said areas sloping up wardly at greater anglesto swing the rays emitted UNITED STATES PATENTS thereby through agreater angle toward the me- Number Name Date man plane. 2,170,912 RalphAug. 29, 1939 THOMAS w. RoLPH. 2,260,693 Ralph oct. 28,1941

REFERENCES CITED The following references are of record in the me ofthis patent:

